228 research outputs found

    Microscopic study of Ca++Ca fusion

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    We investigate the fusion barriers for reactions involving Ca isotopes 40Ca+40Ca\mathrm{^{40}Ca}+\mathrm{^{40}Ca}, 40Ca+48Ca\mathrm{^{40}Ca}+\mathrm{^{48}Ca}, and 48Ca+48Ca\mathrm{^{48}Ca}+\mathrm{^{48}Ca} using the microscopic time-dependent Hartree-Fock theory coupled with a density constraint. In this formalism the fusion barriers are directly obtained from TDHF dynamics. We also study the excitation of the pre-equilibrium GDR for the 40Ca+48Ca\mathrm{^{40}Ca}+\mathrm{^{48}Ca} system and the associated Ī³\gamma-ray emission spectrum. Fusion cross-sections are calculated using the incoming-wave boundary condition approach. We examine the dependence of fusion barriers on collision energy as well as on the different parametrizations of the Skyrme interaction.Comment: 11 pages, 13 figure

    Microscopic Calculation of Fusion: Light to Heavy Systems

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    The density-constrained time-dependent Hartree-Fock (DC-TDHF) theory is a fully microscopic approach for calculating heavy-ion interaction potentials and fusion cross sections below and above the fusion barrier. We discuss recent applications of DC-TDHF method to fusion of light and heavy neutron-rich systems.Comment: 8 pages, 8 figure

    Fusion using time-dependent density-constrained DFT

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    We present results for calculating fusion cross-sections using a new microscopic approach based on a time-dependent density-constrained DFT calculations. The theory is implemented by using densities and other information obtained from TDDFT time-evolution of the nuclear system as constraint on the density for DFT calculations.Comment: 4 Pages, 6 Figures Proceedings of INPC 2013, to be published in EPJ Web of Conference

    Microscopic DC-TDHF study of heavy-ion potentials and fusion cross sections

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    We study heavy-ion fusion reactions at energies near the Coulomb barrier, in particular with neutron-rich radioactive ion beams. Dynamic microscopic calculations are carried out on a three-dimensional lattice using the Density-Constrained Time-Dependent Hartree-Fock (DC-TDHF) method. New results are presented for the 132^{132}Sn+40^{40}Ca system which are compared to 132^{132}Sn+48^{48}Ca studied earlier. Our theoretical fusion cross-sections agree surprisingly well with recent data measured at HRIBF. We also study the near- and sub-barrier fusion of 24,16^{24,16}O on 12^{12}C which is important to determine the composition and heating of the crust of accreting neutron stars.Comment: Talk given by . Volker E. Oberacker at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS

    Dynamic Microscopic Theory of Fusion Using DC-TDHF

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    The density-constrained time-dependent Hartree-Fock (DC-TDHF) theory is a fully microscopic approach for calculating heavy-ion interaction potentials and fusion cross sections below and above the fusion barrier. We discuss recent applications of DC-TDHF method to fusion of light and heavy systems.Comment: Proceedings for the talk presented by A.S. Umar at the Nuclear Structure and Dynamics II, Opatija, Croatia, July 9-13, 201

    Monitoring and Pay: An Experiment on Employee Performance under Endogenous Supervision

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    We present an experimental test of a shirking model where monitoring intensity is endogenous and effort a continuous variable. Wage level, monitoring intensity and consequently the desired enforceable effort level are jointly determined by the maximization problem of the firm. As a result, monitoring and pay should be complements. In our experiment, between and within treatment variation is qualitatively in line with the normative predictions of the model under standard assumptions. Yet, we also find evidence for reciprocal behavior. Our data analysis shows, however, that it does not pay for the employer to solely rely on the reciprocity of employees

    The UN in the lab

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    We consider two alternatives to inaction for governments combating terrorism, which we term Defense and Prevention. Defense consists of investing in resources that reduce the impact of an attack, and generates a negative externality to other governments, making their countries a more attractive objective for terrorists. In contrast, Prevention, which consists of investing in resources that reduce the ability of the terrorist organization to mount an attack, creates a positive externality by reducing the overall threat of terrorism for all. This interaction is captured using a simple 3Ɨ3 ā€œNested Prisonerā€™s Dilemmaā€ game, with a single Nash equilibrium where both countries choose Defense. Due to the structure of this interaction, countries can benefit from coordination of policy choices, and international institutions (such as the UN) can be utilized to facilitate coordination by implementing agreements to share the burden of Prevention. We introduce an institution that implements a burden-sharing policy for Prevention, and investigate experimentally whether subjects coordinate on a cooperative strategy more frequently under different levels of cost sharing. In all treatments, burden sharing leaves the Prisonerā€™s Dilemma structure and Nash equilibrium of the game unchanged. We compare three levels of burden sharing to a baseline in a between-subjects design, and find that burden sharing generates a non-linear effect on the choice of the efficient Prevention strategy and overall performance. Only an institution supporting a high level of mandatory burden sharing generates a significant improvement in the use of the Prevention strategy
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